The present invention relates to implantable spinal devices and methods for their use. More particularly, the present invention relates to rigid interbody devices having an attached ligament.
A variety of interbody implants are available for disc replacement and spinal fusion procedures. These implants have been manufactured of various materials including stainless steel, titanium, composites, allograft, xenograft or other biocompatible materials, and have the necessary strength to prevent the disc space from collapsing. Some types of implants have been developed from bio-compatible materials and incorporate threads on the outer surface of the implant that retain the implant in the disc space after it is threaded therein. Still other implants have been developed that are provided with vertebral engaging surfaces on the upper and lower faces of the implant to resist migration of the implant in the disc space and/or expulsion of the implant from the disc space. Other techniques include the placement of one or more interbody fusion devices in the disc space along with a plate or rigid construct that spans the affected disc space. These rigid constructs can be used to apply a compressive load to the inserted implants to further promote fusion.
One disadvantage with some prior art implants is that the implants or other material placed in the disc space might move or migrate in the disc space, creating a risk of expulsion from the disc space and collapse of the disc space. While threaded implants and implants with vertebral engaging surfaces can provide improved migration resistant capabilities, insertion of these implants into the disc space can be difficult and time-consuming, and the migration resistant capabilities of such implants can be improved.
Other techniques contemplate insertion of one or more implants from an anterior approach to the disc space. This approach can require excision of the anterior longitudinal ligament extending across the disc space. When this ligament is removed, the affected spinal joint could be overextended, resulting in expulsion of the one or more implants from the disc space.
There are also disadvantages with prior art spinal fusion techniques that include insertion of an implant in the disc space and placement of a rigid construct across the subject vertebral level to maintain stability of the segment until fusion has been achieved. One disadvantage is that the installation of these constructs can be time consuming and difficult. Further, the rigid construct is permanently implanted into the body, and inhibits flexure of the joint across which the construct is placed. These rigid constructs can also support too much of the spinal column load, resulting in poor incorporation of the implant.
Therefore, there remains a need for improved spinal implants for applications that require both bearing or compression load carrying capabilities to support the spinal column along with capabilities to resist expulsion of the implant from the disc space.
The present invention is directed to a fusion implant having a rigid portion for insertion between adjacent bony structures and a flexible portion for securement to the adjacent bony structures.
According to one aspect of the invention, there is provided a fusion implant that has a body portion positionable in the disc space between adjacent upper and lower vertebrae. The implant further includes a flexible ligament extending from the body portion along the upper vertebral body and the lower vertebral body.
According to a further aspect of the invention, there is provided a spinal fusion implant that is adapted for insertion into the space between adjacent first and second vertebral bodies. The implant includes a body portion having a first bearing surface for contacting an endplate of the first vertebral body and a second bearing surface for contacting the endplate of the second vertebral body. At least one flexible ligament extends from the body portion so that it can be secured to the first and second vertebral bodies outside the disc space.
According to another aspect of the invention, there is provided a method of inserting an interbody fusion implant. The method includes providing an implant having a rigid body portion with an upper bearing surface and opposite lower bearing surface; accessing the disc space between adjacent vertebrae; inserting the body portion of the implant into the disc space; securing a flexible ligament to the body portion; and securing the flexible ligament to the adjacent vertebrae.
According to a further aspect of the invention, a method of preparing a spinal implant is provided. The method includes obtaining a rigid body portion and attaching a flexible ligament to the rigid body portion. Threads or other bone engaging surfaces can be formed on the body portion.
These and other aspects, advantages, features, embodiments, and objects of the present invention will be apparent to those skilled in the art based on the following descriptions of the illustrated embodiments of the present invention.